Centerless grinding apparatus

ABSTRACT

A centerless grinding machine of the type in which a work piece rests in a pair of yokes and is rotated by a driving wheel, in which the driving wheel is mounted on an arm pivoted to enable the driving wheel to be moved into and out of engagement with the work piece, with the arm having an adjustable weight for varying the pressure of the driving wheel against the work piece.

United States Patent Richard Dec. 31, 1974' [54] CENTERLESS GRINDING APPARATUS 1,864,376 6/1932 Russell 51/236 X 2,195,049 3/1940 Wallace 51/236 X [751 Invent Albert weymuth, 2,939,253 6/1960 Richard 51/103 wn Mass.

[73] Assignee: Richards Micro-Tool Co., Inc., Primary Examiner'1-1ar01d D. Whitehead Plymouth, Mass. Attorney, Agent, or FirmR0bert E. Ross [22] F1led: Nov. 27, 1972 [57] ABSTRACT [211 App! A center less grinding machine of the type in which a work piece rests in a pair of yokes and is rotated by a 52 US. Cl. 51/103 wn, 51/236 driving wheel, in hi the driving wheel is mounted [51] Int. Cl B24b 5/18 7 On an arm pivoted to enable the driving wheel 10 be [58] Field of Search 51/103 R, 103 WH, 236 moved n and out f ngagement with the work piece, with the arm having an adjustable weight for [56] References Cit d varying the pressure of the driving wheel against the UNITED STATES PATENTS Place- 1,452,508 4/1923 Hervig 51/103 R 4 i 7 a g igures 5e 54 T Q t H i so Is 42 as SHEET 20F 5 PATENTED DECS 1 I974 SHEET 3 0F 5 m EQEEWWMHIMA PATENTED m3 1 I974 3,857. 204

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C ENTERLESS GRINDING APPARATUS BACKGROUND OF THE INVENTION In US. Pat. No. 2,939,253 issued June 7, 1960 to the present applicant and another, there is illustrated a centerless grinding machine in which the work piece rests in a pair of yokes and is rotated therein by separate driving means, comprising a wheel having a resilient outer periphery. An end of the workpiece extends beyond one of the yokes into position for engagement with a grinding wheel. The driving wheel rotates the work piece in a direction such that the surface of the work piece and the surface of the grinding wheel move in opposite directions.

In the device disclosed in the above identified patent, the driving wheel is mounted on the forward end of a support arm which is pivoted at a rear portion so that the driving wheel can be moved into and out of engagement with the work piece. The force urging the driving wheel into engagement with the work piece is the weight of the support arm, the driving wheel, and the driving motor, which is mounted on the support arm. The arm is lifted out of engagement with the workpiece by a hydraulic cylinder connected between the arm and the base of the machine. To limit the downward movement of the arm, an adjustable stop is provided, so that the position of the wheel in relation to the resilient surface of the driving wheel may be controlled.

In the use of the machine disclosed in the above identified patent, difficulties have been encountered in obtaining uniform and reliable driving force, particularly on work pieces of small diameter. In such case, the stop means must be carefully adjusted so that excessive pressure is not imparted to the work piece. However, if insufficient force is applied to the piece, the driving wheel cannot rotate the work piece against the drag imparted by the grinding wheel. The delicate adjustment required to achieve adequate driving force without excessive pressure being applied to the work piece is time-consuming and greatly reduces the production capacity of the machine. The difficulty of proper adjustment is increased by the fact that if the periphery of the driving wheel is only slightly out of round much greater pressure is applied to the work piece during certain portions of the wheel rotation, and during other portion, the force may be insufficient to rotate the wheel. It has been found that a wheel out of round by only a few thousands of an inch will not produce satisfactory results.

Another operating difficulty with the machine disclosed in the above identified patent is the fact that the stop means must be re-adjusted for each new diameter of work piece placed in the machine, which further reduces the production rate.

SUMMARY OF THE INVENTION To avoid the above described difficulties, the centerless grinding machine disclosed herein utilizes a novel form of work driving mechanism, in which a support arm which is freely pivoted at a medial portion is provided with a driving wheel and motor at one end and means for adjusting the force with which the driving wheel presses against the work piece. In the illustrated embodiment said means comprises a counterweight slidably mounted on the arm on the side of the pivot opposite to the side on which the driving wheel is mounted. The counter-weight may be moved toward and away from the pivot to decrease and increase, respectively, the pressure of the driving wheel against the work piece. Although a stop is provided to limit the movement of the driving wheel in the direction of the arm, said stop is not normally utilized during a grinding operation, but instead, the driving wheel and support arm is supported only by the work-piece. The driving force therefore does not vary during the rotation of the driving wheel, and any lack of concentricity of the driving wheel does not affect either the driving force or the pressure of the wheel against the work piece, since the arm can move freely up and down during rotation of the driving wheel.

DESCRIPTION OF THE FIGURES OF THE DRAWING FIG. 1 is a view in front elevation of a centerless grinding machine embodying the features of the invention, with the driving wheel in the operating position against the work piece. I

FIG. 2 is a view of a portion of the machine of FIG. 1, with the drivingwheel in the non-operating position.

FIG. 3 is a top plan view of the machine as illustrated in FIG. 1.

FIG. 4 is an enlarged view in side elevation of the work-holding portion and work stop adjusting means.

FIG. 5 is a top plan view of the machine shown in FIG. 4.

FIG. 6 is a view of the portion of the machine shown in FIG. 4 as seen from the left end of FIG. 4.

FIG. 7 is a view of the portion of the machine shown in FIG. 4 as seen from the right end.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT Referring to the drawing, there is illustrated a centerless grinding machine of the type in which the work piece is rotated in suitable supports by a driving wheel separate from the grinding wheel.

The illustrated embodiment of the machine utilizes certain basic components which are common to centerless grinders now in commercial use. As illustrated in FIG. 1, the machine comprises a base 10 having a bed 12 on the upper surface and carrying a mount 14 for a grinding wheel 16 and a grinding wheel motor 18. The bed is longitudinally and transversely adjustable relative to the grinding wheel by conventional mechanisms operated by hand wheels 20 and 22.

A support 24 for the work supporting and rotating mechanism is disposed on the bed and is so mounted thereon as to enable the mechanism to be moved longitudinally on the bed and rotated thereon in relation to the horizontal axis thereof.

In order that the work may be supported in a desired manner the top of the support 24 has a horizontal way 26 onto which is slidably mounted a block 28 carrying a vertically extending work holder 30 having a V- shaped recess 32 for receiving a work piece, and the end of the support 24 is provided with a vertical way 34 onto which is slidably mounted a block 36 carrying a second vertically extending work holder 38 having a V-shaped recess 40 for receiving the work piece.

The block 28 is slidable horizontally to accomodate which comprises a stop bar 42 clamped in a holder 44 mounted on a longitudinally adjustable block 46. The holder 44 is secured to the block 46 by a bolt 48 extending through an arcuate slot 50 in the holder 44. The holder is therefore adjustable by being rotatable about the bolt 48 as a center and rotatable about the center of the arc of the arcuate slot, to enable the stop bar 42 to be positioned on the centerline of work pieces of various sizes.

During operation, the workpiece rests in the V- shaped recesses 32 and 40 with an end or other portion thereof to be ground in contact with the rotating grinding wheel 16. The work piece W is rotated in said recesses in the same direction as the grinding wheel so that the'contacting surfaces thereof are moving in opposite directions. I

The work piece W is rotated by means now to be de scribed. A fixed support arm 52 is mounted on the support 24 and is inclined upwardly therefrom in a direction away from the grinding wheel. A movable arm 54 is mounted at its media] portion to the end of the fixed arm 52 at pivot 56. The movable arm 54 carries at one end a driving wheel 58 and driving motor 60, and

carries on its upper surface a weight adjusting block 62, slidably mounted in a longitudinal slot 64.

The arm 54 is movable about the pivot between an upper or non-operating position as shown in FIG. 2 and a lower or operating position as shown in FIG. 1, and is so positioned that when the arm is in the operating position, the driving wheel contacts the work piece between the work holders 30 and 38. The axis of the driving wheel is inclined in relation to the axis of the work piece in the usual manner so that the rotation of the driving wheel not only rotates the work piece, but also imparts an end thrust thereto so that the work piece is held firmly against the end of the stop bar 42 during the grinding operation. 7

The pressure with which the driving wheel bears against the work piece may be readily adjusted by moving the block 62 along the arm 54. On work pieces of small diameter the block may be a considerable distance to the left (as seen in FIG. 1) of the pivot 56 so that an appreciable portion of the weight of the motor 60 and driving wheel 58 is counterbalanced by the weight, and the wheel 58 bears against the work piece with only a slight pressure.

When larger work pieces are being ground, the weight 46 will be nearer the pivot, so that less of the weight of the motor and driving wheel is counterbalanced, and the driving wheel bears against the work piece with greater pressure.

In the case of extremely large work pieces, it may be desired to move the block 62 to the right of the pivot so that a portion of the weight of the block is added to the weight of the motor and driving wheel, to increase the pressure against the work piece. The position of the block 62 for any particular desired pressure of the driving wheel against the work piece will, of course, depend on the relative weights of the components.

However, whatever the position of the block, the pressure of the driving wheel against the work piece remains constant throughout the revolution of the driving wheel, even though the wheel may not be perfectly circular, since the arm 54 is supported only by the work piece and is free to move up and down during the rotation of the driving wheel as necessary to accomodate any lack of concentricity of the wheel periphery.

The balance of the arm 54 also makes it easy for the machine operator to lift the arm to replace the work piece, without any power assistance being necessary.

When it is desired to temporarily stop the operation of the machine the arm 54 may be lifted and retained in the upper position by placing a stop pin 66 in an aperture inthe support arm.

Although in the illustrated embodiment the work holders are spaced elements with V-shaped recesses, it will be understood that other forms of work holders may be used. A

Since certain changes in the illustrated device will be apparent to one skilled in the art, without departing from the scope of the invention, it is intended that the matter contained herein be interpreted in an illustrative and not a limiting sense.

I claim:

1. A centerless grinding apparatus especially adapted for a thin, flexible work piece comprising a base, a pair of spaced-apart work supports on the base for receiving a cylindrical portion of the work piece, a grinding wheel adapted to operate upon a portion of the work piece extending beyond the work supports, a balanced arm medially pivoted on the base, a driven driving wheel rotatably supported on one end of the arm and adapted drivingly to engage the portion of the work piece between the supports, means on the other end of the arm for counterbalancing the arm and means for adjusting the position of the counterbalancing means to vary the force with which the driving wheel engages the work piece in full floating engagement, whereby the bearing force of the driving wheel is sufficient to drive without distorting the work piece.

2. A centerless grinding apparatus according to claim 1 further characterized in that the counterbalancing means includes a counter weight on the arm movable to adjust its spacing from the pivot.

3. A centerless grinding apparatus according to claim 1 further characterized in that the pivoted arm is movable to withdraw the driving wheel into widely separated relationship with the work piece.

4. A centerless grinding apparatus according to claim 1 further comprising driving means on the arm connected to the driving wheel. 

1. A centerless grinding apparatus especially adapted for a thin, flexible work piece comprising a base, a pair of spacedapart work supports on the base for receiving a cylindrical portion of the work piece, a grinding wheel adapted to operate upon a portion of the work piece extending beYond the work supports, a balanced arm medially pivoted on the base, a driven driving wheel rotatably supported on one end of the arm and adapted drivingly to engage the portion of the work piece between the supports, means on the other end of the arm for counterbalancing the arm and means for adjusting the position of the counterbalancing means to vary the force with which the driving wheel engages the work piece in full floating engagement, whereby the bearing force of the driving wheel is sufficient to drive without distorting the work piece.
 2. A centerless grinding apparatus according to claim 1 further characterized in that the counterbalancing means includes a counter weight on the arm movable to adjust its spacing from the pivot.
 3. A centerless grinding apparatus according to claim 1 further characterized in that the pivoted arm is movable to withdraw the driving wheel into widely separated relationship with the work piece.
 4. A centerless grinding apparatus according to claim 1 further comprising driving means on the arm connected to the driving wheel. 